In an LTE system, downlink data receiving at a mobile terminal includes Physical Downlink Control Channel (PDCCH) receiving. A PDCCH carries Downlink Control Information (DCI) of one or more mobile terminals. The DCI generally includes downlink scheduling and allocation information used in demodulating and decoding a Physical Downlink Shared Channel (PDSCH) when a mobile terminal receives the PDSCH, scheduling authorization information of sources and transmission format used in the mobile terminal transmitting data in a Physical Uplink Shared Channel (PUSCH), acknowledgement information transmitted in a shared channel, and uplink physical channel power control information.
A mobile terminal can blindly detect DCI in a received PDCCH based on a Radio Network Temporary Identifier (RNTI) value which is configured for the mobile terminal, decode the DCI and make configuration for receiving a PDSCH or sending a PUSCH based on the decoded PCI.
When receiving the PDCCH and blindly detecting the DCI, the mobile terminal needs to perform a Cyclic Redundancy Check (CRC) on a demodulation result in each search space, and match the demodulation result to the configured RNTI value. If the demodulation result matches the configured RNTI value, the corresponding DCI is determined to be DCI actually sent to the mobile terminal. According to LTE specifications, a mobile terminal can match 22 search spaces at most and one search space can detect data of one or two DCI length. That is, CRC and RNTI matching may be performed 44 times at most.
However, in LTE specifications, a 16-bit CRC is employed to save bits transmitted in a PDCCH. Too few CRC check bits may result in a certain degree of mismatching. Theoretically, a misdetection of DCI may occur every 1.5 seconds if RNTI matching is performed 44 times in each sub frame.
The misdetection of DCI may further lead to wrong configuration for reception of PDSCH or transmission of PUSCH, which will cause received downlink data to be discarded or downlink data to be wrongly transmitted and received. This, in turn, may result in package loss and reduce the throughput of the mobile terminal system. Besides, the wrong configuration may also cause the system abnormal and reduce the reliability and stability of the mobile terminal system.
In some technologies, a determination process is performed on whether DCI obtained by blind detection is valid or not. If it is determined that invalid information exists in parameters configured in a PDSCH or a PUSCH, the DCI is filtered out to avoid system instability resulted from abnormal configuration. However, it still happens that some DCI obtained by misdetection cannot be filtered out, especially when DCI obtained by misdetection is valid in itself, while the DCI is not the information that a base station actually sends to a mobile terminal.
In some technologies, in order to filter DCI, a threshold is set for a distance on a state machine shortest path output from convolutional decoding when DCI demodulation is performed. However, by this method, it often happens that the DCI that a base station actually sends to a mobile terminal is filtered out, while the DCI obtained by misdetection is retained.
Therefore, new DCI detection methods are needed to reduce the probability of DCI misdetection.